Refactors dependency injection and configuration management

Replaces global singleton configuration with dependency injection
Introduces more modular and testable approach to configuration
Removes direct references to calendarConfig in multiple components
Adds explicit configuration passing to constructors

Improves code maintainability and reduces global state dependencies

test/utils/DateService.test.ts

@@ -1,11 +1,13 @@
 import { describe, it, expect, beforeEach } from 'vitest';
 import { DateService } from '../../src/utils/DateService';
+import { CalendarConfig } from '../../src/core/CalendarConfig';
 
 describe('DateService', () => {
   let dateService: DateService;
 
   beforeEach(() => {
-    dateService = new DateService('Europe/Copenhagen');
+    const config = new CalendarConfig();
+    dateService = new DateService(config);
   });
 
   describe('Core Conversions', () => {